The field of the invention is the monitoring of the state of the tires as a function of the parameters of temperature and of pressure of these tires, in particular in the motor vehicle field. The tire pressure detection systems, known by the name TPMS (the initials of Tire Pressure Monitoring System) or SSPP (the initials for “Système de Surveillance de la Pression des Pneus” (in French)), comprises temperature and pressure sensors located in each tire, for example on the rim, and a central processor unit for processing the data supplied by these sensors by radio transmission.
In the event of leakage, these sensors supply the driver with information on the state of the tires with the aid of a display based on the processing of the data. Alarm means are triggered when this state corresponds to parameter values that go beyond a ceiling or fall below predefined thresholds.
In order to allow the detection of air leakages in a tire, whether they be slow or fast, various techniques for monitoring the pressure of this tire have been developed. It is known for example from patent EP 0 786 361 to monitor the inflation pressure (and/or a characteristic parameter), while safeguarding the pressure-drop measurements in several ways: by comparing the pressure data of several wheels with one another, by measuring the pressure regularly several times over different time periods, and by using a statistical method called “regression lines” calculated on the basis of these measurements. This solution requires long measurement periods and does not use the temperature compensation of the pressure measurements.
It is also known, for example from patent FR 2 871 736, that the detection of air leakages can advantageously be carried out by compensating for the value of the pressure with that of the temperature, and by comparing it with a threshold. This method makes it possible to quickly obtain results but it does not involve noise filtering and the risk of false alarms is thus not eliminated.
Patent FR 2 900 099 furthermore proposes to monitor the temperature-compensated pressure while neutralizing the alarms if the temperature variation per unit of time is less than a threshold value, provided that the pressure remains sufficient. But when the temperature does not vary very much, this approach can generate false alarms.
In general, the methods of the prior art culminate in the appearance of false alarms, despite the improvements made in the speed of detection.